The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, HDDs have been desired to store more information in its limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
In particular, the dimensions of the recording head in the cross-track direction and in the throat height direction need to be minimized. When this is done, the volume of the pinned layer is reduced and problems arise in regard to performance fluctuation of the read element. In order to avoid this, conventionally performance stability is ensured by providing sufficient volume by extending the pinned layer in the throat-height direction.
Also, processing to form the track width of the read head with very small size and high accuracy is employed prior to forming the throat height. The reason for this is that performing fine patterning when there is little difference in surface level is advantageous in regard to increasing fineness and precision in the photolithographic step and other subsequent steps.
The following problems arise when a read head is manufactured with a pinned layer that is extended in the throat height direction combined with the conventional technique of forming the track width of the read head beforehand. In the track width direction of the read element, a film referred to as a hard bias layer that is used for stabilizing the magnetic characteristic of the read element is typically provided. This hard bias layer remains behind the read element and has the same cross-sectional structure as the pinned layer. In these circumstances, two chief problems arise.
The first problem is that, since the hard bias layer has the same cross-sectional structure as the pinned layer, and the hard bias layer is longer in the throat height direction than in other typical structures, the shape anisotropy effect is lowered, resulting in a degradation in the ability to withstand external magnetic fields. The second problem is that the rear portion of this hard bias layer that is left behind the read element actually applies a biasing magnetic field to the pinned layer, which has an adverse effect on this pinned layer.